I'm making an animal game where a tiger attacks up close with a set animation "fangs"

I checked the tutorial http://www.scirra.com/tutorials/386/how-to-make-a-player-atack however after i use the atk on an enemy the attack freezes on its last frame and continues with the same animation when i press left or right until i release the left/right key on my keyboard sorry kind of confusing to explain...